Sherardia arvensis L.
CC = *
CW = 5
MOC = 17
Family - Rubiaceae
Habit - Annual forb, usually minutely roughened or pubescent throughout with wavy, soft hairs
Stems - Sprawling to loosely ascending from a spreading base, sometimes forming loose mats, 4-angled, the nodes sometimes ringed with dense, short hairs.
Leaves - Sessile, in whorls of 6. Leaf blades 4-20 mm long, 1.5-3.0 mm wide, narrowly elliptic to nearly linear, angled at the base, angled to a sharply pointed tip, the margins entire, flat to slightly rolled under, glabrous or minutely roughened or hairy, the upper surface glabrous to slightly roughened or sparsely soft-hairy, the undersurface soft-hairy, not glandular, the venation with only the midvein visible.
Inflorescences - Terminal and axillary, small headlike clusters closely subtended by whorls of 6 or 8, small, leaflike, involucral bracts. Flowers sessile or nearly so, 2-4 per cluster. Peduncles to 1 cm long in fruit, 1-2 mm long in flower, 4-angled.
Flowers - Calyces 0.5-1 mm long, minutely 4-lobed, the lobes triangular. Corollas 4-lobed, 4.0-5.5 mm long, trumpet-shaped, the slender tube well-developed, longer than the 4 spreading lobes, pink, glabrous, the lobes not overlapping in bud. Stamens 4, attached in the corolla throat, the anthers exserted. Filaments white, glabrous, 1.1 mm long. Anthers purplish, 0.3 mm long. Style exserted, unequally 2-branched, the stigmas capitate. Ovary fully inferior, 1-locular, the ovules 1 per locule.
Fruits - schizocarps, 1-2 mm long, 2-4 mm wide, 2-lobed, slightly rectangular in cross-section, splitting from the base into 2 mericarps, these globose or nearly so, indehiscent.
Flowering - April - June.
Habitat - Glades, ledges of bluffs, streambanks, pastures, cemeteries, fields, lawns, gardens, sidewalks, roadsides, and open, disturbed areas.
Origin - Native to Europe.
Lookalikes - Species of Galium.
Other info. - This little introduced species was first collected in Missouri in 1946, and was considered rare in the state at the time of Steyermark's seminal Flora of Missouri publication in 1963. Its abundance is rapidly increasing, mostly but not exclusively in the far southern reaches of the state. It is easily identified by its whorled leaves on square stems and clusters of tiny pink flowers. It is closely related to species of Galium and is very similar to them in appearance; however, there are no Missouri species of Galium with pink flowers. In addition, plants in the Galium genus lack the well-developed (but tiny!) corolla tube present in Sherardia arvensis. The plant can be quite weedy, having a particular affinity for mowed lawns, and will undoubtedly continue to expand its range in Missouri.
Photographs taken somewhere in North Carolina, 4-20-03, and in Auburn, AL., 5-14-05 (DETenaglia); also near Labadie, Franklin County, MO, 5-9-2014 and 5-8-2020 (SRTurner).